Fritz



March 10, 1964 FRITZ HOT BLAST HEATER 3 Sheets-Sheet 1 Filed May 11, 1962 INVENTOR.

LEONARD FRITZ ATTORNEYS March 10, 1964 L. FRITZ HOT BLAST HEATER 3 Sheets-Sheet 2 Filed May 11, 1962 INVENT O R.

LEONARD FRITZ BY Gum) 136mm ATTORNEYS March 10, 1964 FRITZ HOT BLAST HEATER 3 Sheets-Sheet 3 Filed May 11, 1962 INVENTOR.

LEONARD FRITZ ATTORNEYS 3,124,337 HGT BLAST HEATER Leonard Fritz, Beileville, Mich, assignor to Huron Valley Steel Corporation, Belleville, Mich. Filed May 11, 1962, Ser. No. 193,957 1 Claim. (Cl. 263-49) This invention relates to a hot blast heater and more particularly, a heater useful for heating air and other gases to high temperature for use in metal treating furnaces such as blast furnaces and the like.

In the use of metal treating furnaces, such as blast furnaces, cupola furnaces and the like, large quantities of heated air or oxygen or other gases are required. Various types of heaters have been used to heat the required gases. These prior heaters uniformly have two important disadvantages: first, the temperature of their output gases is relatively low, and second, they are extremely expensive, particularly since they require relatively high pressure compressors and high pressure construction.

Accordingly, it is an object of this invention to provide a hot blast heater capable of heating large quantities of air, oxygen and other gases to high temperatures previously unattainable in commercially available equipment, with the cost of construction and operation of the heater being but a small fraction of that of prior heaters.

A further object of this invention is to provide a hot blast heater which utilizes, as a heat transfer medium, a long, wide, shallow filler or bed formed of small size pieces of refractory material, the filler being alternately heated and then used to heat gases passed through it at unusally low pressures, and the heater using a low pressure gas blower or compressor to move the gases through the heater and being of a low pressure construction.

These and other objects and advantages of this invention will become apparent upon reading the following description, of which the attached drawings form a part.

In these drawings:

FIG. 1 is a top plan view of the hot blast heater herein.

FIG. 2 is a side elevational view thereof, and

FIG. 3 is a front elevational view.

FIG. 4 is a cross-sectional elevational View of one of the heater tanks taken in direction of arrows 4-4 of FIG. 3.

FIG. 5 is a cross-sectional elevational view of the other heater tank taken in the direction of arrows 55 of FIG. 3, and

FIG. 6 is a cross-sectional view taken in the direction of arrows 6-6 of FIG. 5.

The hot blast heater generally designated as It), is preferably formed of two, substantially identical, heater tanks 11 and 12, although for certain purposes, only one tank may be used, while for other purposes it may be desirable to use more than two tanks.

The tanks are each formed of a thin, sheet metal, elongated, horizontally arranged, cylinder 14 having closed ends, and whose length is preferably more than twice its diameter. The interior walls thereof are lined with a refractory fire brick 15. Extending the length of the tank, at the bottom thereof, is a sheet metal duct or manifold 16 having a perforated top wall 17, the perforations being of a size which permits passage of gas but prevents passage of small size solid particles.

The tanks are each partially filled with a filler or bed F formed of loosely piled small size pieces of a refractory material and preferably, refractory fire brick crushed into irregular shaped pieces ranging in size from approximately one-quarter of an inch to approximately one-half inch. The size of these pieces are not critical and may be varied somewhat. The pieces are spread over the bottom of each tank to a uniform depth to form a long, wide,

3,ll24,337 Patented Mar. 10, 1964 shallow, loose bed whose depth is preferably less than one-half the diameter of the tank.

A cold gas inlet 18, which opens into duct 16, is formed at the bottom center of each tank. Connected to the inlet is a cold gas riser 19 having a cold gas control valve 20; the valve being schematically shown in the drawmgs.

Opening into the riser 19 is a combustion gas exhaust outlet 21 connected to an exhaust stack 22 and having a valve 23 (schematically shown) for blocking the flow of exhaust gases therethrough.

At the top of each tank, near one end thereof, is a hot gas outlet 25 to which is connected a hot gas conduit 26 which may be closed off at each tank by a valve 27 (schematically shown). At the opposite end of each tank, near the top thereof and above the level of the filler F, is a conventional, oil or gas, flame type heater. The heater, which has a flame nozzle 31 extending into the tank, is supplied with fuel through a fuel supply line 32 and with air or the like for combustion through a supply pipe 33 connected to a hollow jacket 34 which surrounds the nozzle. The heater, when operated, provides a flame 35 near the top of the tank (see FIG. 4).

The cold gas supplied to the system, which in most cases would be air, is supplied through a low pressure blower or compressor 4%, which blows the supply gas through a cold gas conduit 41, to which the risers 19 are connected. Also connected to conduit 41, is a cold gas supply pipe 42, having its opposite end connected to horizontal pipe 43, connected in turn to the combustion gas inlet pipes 33, to thereby supply gas, such as air, to the heaters for combustion purposes. Pipes 33 are provided with shut-off valves 44 (schematically shown).

A second cold air supply pipe 45 is connected to the cold air conduit 41 and also to the hot air conduit at 46. It is provided with a mixing valve 47 (schematically shown) to supply varying amounts of cold air into the hot air conduit to thus maintain predetermined temperatures of the heated gas which feeds through feed tube 48, connected to the center of the U-shaped hot air conduit 26, to the furnace.

All of the valves described here may be convention, manually operated valves or conventional remotely controlled electrically operated valves, all of which are readily available.

Operation In operation, the filler in one tank is heated, while the already heated filler in the other tank heats the gas. Then the tanks alternate in this operation. Hence, in tank 11 (see FIG. 4) heater 3:0 is operating to produce a flame 35 and hot combustion gases which travel through the filler (see arrows), thereby heating the filler pieces, and out through the perforated top wall 17 of the duct 16 and then out through the combustion gas exhaust 21 and the exhaust stack 22. Combustion gas exhaust valve 23 is open as is valve 44, but cold gas inlet valve 2% and hot gas outlet valve 27 are closed. This continues until the filler reaches a predetermined temperature.

Meanwhile, in tank 12 (see FIG. 5) the flame heater 30 is turned off, cold gas inlet valve 20 and hot gas outlet valve 27 are both open and cold gas flows in through duct 16, is evenly distributed, through the perforated top wall 17 of the duct, to the filler. The gas passes through the voids in the filler, is heated, and then passes out through hot gas conduit 25 and feed tube 48 to the furnace. The temperature of the hot gas is regulated by the addition of cold gas from pipe 45.

After a predetermined time the two tanks alternate operation, thereby providing a continuous flow of heated gas.

In the construction described above, the resistance to gas flow, called back pressure, caused by the widely spread out filler is so low and the flow of gases therethrough is so widely dispersed, that the blower need provide only a small amount of pressure to force gases through the system. For example, in a commercial embodiment constructed and operated to supply hot air to a blast furnace, the tank, which was about eighteen feet in length and about eight feet in diameter and which was slightly less than half filled with fire brick crushed to onequarter to one-half inch size irregular shaped pieces operated properly with air pressure at the cold air inlets 18 being at about one pound above atmospheric pressure. The pressure drop across the filler, when cold, was 4 oz., and when fully heated varied between 12 and 14 oz.

Despite such low pressure, the heater delivered approximately 10,000 cubic feet of. air per minute to a maximum of 2800 F., and regulated by cold air mixing to the range of 1800 F. to 2000 F. T e B.t.u. input and recovery ranged from 90% to 92% in efficiency. The tanks were cycled to alternate operation at about ten minute intervals. Such temperatures cannot be obtained with conventional hot blast heaters and heaters which supply one half and less of that temperature range and require high pressure blowers and high pressure tank and piping construction which are many times more costly than that required here.

While this invention was conceived primarily to supply super-heated air to a blast furnace, it may be used for other types of furnaces and for other devices where hot air or other hot gases are needed.

This invention may be further developed within the scope of the following attached claim. Accordingly, it is desired that the foregoing description be read as being merely illustrative of an operative embodiment of this invention and not in a strictly limiting sense.

Having described an operative embodiment of this invention, I now claim:

A low pressure, hot blast heater comprising an elongated cylindrical tank having closed ends and arranged on its side with its axis horizontal;

an elongated, narrow duct extending the full length of the lowermost part of the tank wall parallel to the axis of the tank, and having a perforated top opening into the tank for substantially its full length;

a loose filling formed of small pieces of refractory material filling the lower part of the tank about one-half full and covering said duct top, the filling being semicircular in cross-section and the space in the tank above the filling likewise being semi-circular in crosssection, but inverted relative to the filling;

an exhaust conduit opening into said space at the top of the tank;

a combustion type heater located in the tank space above the filling for providing heated combustion gases in such space for flow of same down through the filling and out through said duct;

an opening in said duct for exhausting said combustion gases from the duct;

a conduit opening into said duct for the flow of cold gas into and through the duct and then up through the filling and into the space above it and out through the exhaust conduit whereby the heated filling will heat the cold gas;

and means for alternating the operation of said heater means and the flow of hot gas down through the filling for heating it and the flow of cold gas to be heated by passing same up through the filling.

References Cited in the file of this patent UNITED STATES PATENTS Re. 19,757 Royster Nov. 12, 1935 1,823,358 Haven Sept. 15, 1931 1,941,446 Isley Dec. 26, 1933 2,470,578 Royster May 17, 1949 2,532,335 Royster Dec. 5, 1950 2,612,364 Peck et al. Sept. 30, 1952 2,655,366 Stanley Oct. 13, 1953 2,944,806 Carter July 12, 1960 

